1. Field of the Invention
The present invention relates to a small-sized line-shaped antenna for use in terminal apparatuses such as a cellular phone, portable information terminal, and radio local area network (LAN).
2. Description of the Background Art
A line-shaped antenna (hereinafter referred to simply as the “antenna”) includes, for example, a conductor in which an antenna element is formed in a meander form (hereinafter referred to sometimes as the “meander antenna”). Usually, the antenna element of the meander antenna is formed by etching a pattern of a metal plate attached to a dielectric substrate or by punching the element from the metal plate. Therefore, the antenna element is a thin strip-shaped conductor which has a certain degree of width.
However, when the number of bends of the strip-shaped conductor increases, the meander antenna tends to have a narrowed bandwidth.
Moreover, as the above-described line-shaped antenna, an antenna of the antenna element formed integrally with a resin molded material is known. The line-shaped antenna is manufactured by an insert molding. In the insert molding, the antenna element is set in a cavity of a mold, and a resin is injection-molded. When the antenna element has a meander pattern (the conductor has a thin strip shape) punched or etched from the thin metal plate as described above (all patterns are meander patterns in some case and some of the patterns are meander patterns in other case), and when the line-shaped antenna is manufactured in the above-described method, the meander pattern is easily deformed by a flow of resin during the injection molding.
To solve the problem, the antenna element is formed as follows. An integral conductor pattern is formed such that the antenna element is connected to a broad frame provided outside the element via a large number of connection portions. Moreover, to perform the injection molding, the frame and connection portions are held by the mold so that the meander pattern is not deformed.
However, when the meander pattern is complicated, the meander pattern cannot be connected to the frame via the connection portion in a certain portion, and the corresponding portion is easily deformed.
To prevent the meander pattern from being deformed, it is effective to broaden the width of the strip-shaped conductor or increase the thickness thereof. However, there is a problem that a resonance frequency rises.